MAX9776EVKIT+ Maxim Integrated Products, MAX9776EVKIT+ Datasheet - Page 24

• Manufacturer Part Number: MAX9776EVKIT+
• Description: EVALUATION KIT FOR MAX9776
• Manufacturer: Maxim Integrated Products
• Series: DirectDrive™r

Specifications of MAX9776EVKIT+

• Amplifier Type: Class D
• Output Type: 1-Channel (Mono) with Stereo Headphones
• Max Output Power X Channels @ Load: 1.5W x 1 @ 4 Ohm; 60mW x 2 @ 16 Ohm
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Board Type: Fully Populated
• Utilized Ic / Part: MAX9776
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

if the right and left volume controls are set for a maxi-
mum gain 0dB (11111 in Table 7, IN+6dB = 0 from Table
10) before the 3D effect is activated, the volume control
should be programmed to -6dB (11001 in Table 7)
immediately after the 3D effect has been activated.
The audio inputs of the MAX9775/MAX9776—INA, INB,
and INC—are preamplified and then mixed by the input
mixer to create three internal signals: Left (L), Right (R),
and Mono (M). Tables 5a and 5b show how the inputs
are mixed to create L, R, and M. These signals are then
independently volume adjusted by the L, R, and M vol-
ume control and routed to the output mixer. The output
mixer mixes the internal L, R, and M signals to create a
variety of audio mixes that are output to the headphone
speaker and mono receiver amplifiers. Figure 6 shows
the signal path that the audio signals take.
Signal amplification takes place in three stages. In the
first stage, the inputs (INA, INB, and INC) are pre-
amplified. The amount by which each input is amplified
is determined by the bits INA+20dB (B4 in the Input
Mode Control Register) and IN+6dB (B3 in the Global
Control Register). After preamplification, they are mixed
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
Figure 7. Signal Path
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______________________________________________________________________________________
INPUT
INPUT B AND C:
PREAMPLIFIER
0dB, 6dB, 20dB
INPUT A:
0dB, 6dB
MIXER
INPUT
Signal Path
MONO
MONO+6dB
0dB TO 6dB
in the Input Mixer to create the internal signals L, R,
and M.
In the second stage of amplification, the internal L, R,
and M signals are independently volume adjusted.
Finally, each output amplifier has its own internal gain.
The speaker, headphone, and mono receiver amplifiers
have fixed gains of 12dB, 3dB, and 3dB, respectively.
The MAX9775/MAX9776 feature current limiting and
thermal protection to protect the device from short cir-
cuits and overcurrent conditions. The headphone
amplifier pulses in the event of an overcurrent condition
with a pulse every 100µs as long as the condition is
present. Should the current still be high, the above
cycle is repeated. The speaker amplifier current-limit
protection clamps the output current without shutting
down the output. This can result in a distorted output.
Current is limited to 1.6A in the speaker amplifiers and
170mA in the headphone and mono receiver amplifiers.
The MAX9775/MAX9776 have thermal protection that
disables the device at +150°C until the temperature
decreases to +120°C.
-75dB TO 0dB
-75dB TO 0dB
RVOL
LVOL
Current-Limit and Thermal Protection
-75dB TO 0dB
MVOL
OUTPUT
MIXER
12dB
3dB
3dB
SPEAKER
HEADPHONE
RECEIVER